1. Field of the Invention
The present invention relates to a technology for optical color division, which can provide a light source of a desired color for image displaying and capturing.
2. Description of Related Art
The color of an image is generally formed by a plurality of primary color lights and variations in gray scales of the primary color lights. Most commonly used primary color lights are, for example, red (R), green (G), and blue (B).
In a flat display, a back light source is often used with a liquid crystal spatial light modulator and color filters (CFs) in order to present true-color images. An image sensor in a digital camera also needs CFs, and calculates the color differences to present the original color of an object. In a large-size system such as a color video camera and a rear-projection television, three-piece or two-piece prism sets or CFs are employed with a collimated light source in order to present true-color images. When the system uses a CF, each colored pixel on the CF can only present a single primary color of the three primary colors, that is, red, green and blue (RGB), and approximately two thirds of the energy of the incident white light will be absorbed, thereby reducing the optical efficiency of the system and shortening the service life of the battery. Moreover, the manufacturing process of the CFs is complex, and at least one lithography process must be performed on semiconductors for each primary color, resulting in a high cost.
Therefore, in the conventional art, manufacturers or designers in related arts proposed solutions in which the three primary colors of RGB are separated through optical light splitting, thereby avoiding the use of the CFs.
U.S. Pat. No. 5,615,024A discloses an optical structure for replacing the CF, which mainly utilizes a blazed grating to separate the three primary colors. When applied to a panel, each primary color is corresponding to one pixel (mainly a transmitted and diffracted light of the first order). Since the transmitted and diffracted light at the first order is used and a large angle is formed between an incident light and an emergent light, the incident light must enter the blazed grating at a large angle such that the emergent light enters the liquid crystal layer perpendicularly. If a perpendicular incident light enters the blazed grating, the emergent light can only enter the liquid crystal layer at a large angle, thereby limiting the applicability.
In addition to the above conventional art based on optical elements, many other designs have been proposed. However, the optical structures of the CFs in the conventional art have their own advantages and disadvantages. The light-splitting technologies based on optical elements are still researched and developed in order to achieve the best performance.